In this article, we are going to talk about an aquaponics system known as “aquaponics with a flood and drain table.” This is a system that uses clay pebbles, lava rocks, and various types of gravel. The advantage is having a solid substrate that allows the root system to establish itself and keep the plant upright.

These systems are well oxygenated because they operate on a flood and drain cycle, meaning the grow bed fills and then empties. Typically, it works just like a bell siphon.

Advantages of this system

The first advantage of this type of system compared to others is that the gravel and clay pebbles provide support for the plants. If they can grow properly, as they would in soil, we can grow all types of crops, including almost anything grown in the ground, including trees.

The second advantage is that the clay pebbles act as a biofilter. In fact, these pebbles serve both as biofilters for the nitrogen cycle and as a refuge for the bacteria involved in mineralization. The surface area provided by these clay pebbles is therefore extremely useful.

In other systems, a physical support is needed for the bacteria to grow and establish themselves, whereas in this type of system, the growing medium itself provides the surface area for all these bacteria. All the bacterial colonies become part of the growing medium, creating a built-in biofilter. There is no need to buy one, so it is convenient and cheaper!

The second important process in aquaponics is mineralization

Mineralization involves extracting all the minerals that plants need. In aquaponics, fish produce waste that contains organic matter. When you feed your fish pellets, you are also providing organic matter. Bacterial colonies then develop to break down this organic matter into minerals. We are therefore moving from an organic world to a mineral one. The advantage is that once these minerals have dissolved in the water, the plants can absorb them.

It is also worth noting that in a flood and drain system, it is not always necessary to filter out solids. Sometimes, it is easier to add inexpensive auxiliary systems, such as a swirl filter. The water from the fish tank enters on the left, impurities settle at the bottom, and the filtered, purified water flows out to the plants.

We can also use other types of mechanical filtration, such as filter pads.

The idea is that we can place filter pads on top of the clay pebbles, allowing the incoming water to be filtered before returning to the plants. However, one disadvantage of this type of system is that it is stationary. Once it is set up, it cannot be moved every day. Keep in mind that 1,000 liters of water weighs 1,000 kg. So, it is certain that we will not be moving it anymore.

The question is also whether we want to move our system. Probably not, except during major maintenance periods, every year or two. In winter, when everything is slowed down, we may also want to either enlarge it or move it to suit our needs.

Other disadvantages of the flood and drain system

It is important to know that the growing medium is expensive. The cost will depend on what you choose to buy, but it will generally be clay pebbles. When you visit websites online, you will find that clay pebbles cost around €20 for 50 liters. Typically, a grow bed holds 300 liters. This means you will spend six times €20, or between €120 and €140, which is quite expensive.

Furthermore, you cannot necessarily use gravel collected from a riverbank, as the type of rock can significantly affect the pH. You must use a substrate that is pH-neutral.

Another disadvantage is that this type of system takes much longer to plant or harvest than other types of crops. This can be a drawback if you are running a commercial aquaponics operation.

Conclusion

In conclusion, we can say that this type of flood and drain system is ideal for beginners because it is an all-in-one solution. You can grow everything without having to worry about the biofilter for the nitrogen cycle or mineralization, as all of this happens automatically. It is a system that does not require special attention. This means that if your pump unfortunately stops working for a day, there will probably still be water in your grow bed, so your fish will not die. Nitrites and ammonia will not skyrocket in a single day.

You will not be using a vertical growing system with hoses that can become clogged, nor will you have the typical water leaks associated with flood and drain systems. The risk of water leaks is therefore limited, and overall, this is a system that will help you avoid mistakes and prevent future disappointment.

Finally, another advantage is that you will find several kits available on the market at reasonable prices. So, if you are not necessarily a handyman or plumber, you can easily buy a pre-assembled kit that will quickly introduce you to the wonderful world of aquaponics.